DESCRIPTION: Human CMV (HCMV) is a frequent opportunistic pathogen, causing extensive morbidity and mortality. It is a particular problem in AIDS patients, and may be a cofactor for HIV pathogenesis. A better understanding of the molecular mechanisms of HCMV DNA replication and their regulation is needed to aid in developing antiviral strategies. Lytic-phase DNA replication requires both a genetically defined cis-acting replicator, oriLyt, and trans-acting factors such as the virus-specified DNA polymerase. Previous studies led to the development of a model for the mechanism of HCMV oriLyt initiation; in this model a transcript facilitates the assembly of the pre-initiation complex by promoting strand-separation within oriLyt. The specific aims of this proposal are: 1) to better establish the structures of essential elements within the oriLyt sequence using standard molecular genetic approaches; 2) to determine the cis-acting elements involved in regulating oriLyt transcript expression, and identify their cognate activators; 3) to test the applicant s initiator transcript model of the mechanism of initiation; and 4) to test the role of IE2/oriLyt interactions in replicator function.